Reconfigurable communication device and method

ABSTRACT

A communication device includes a transmitter operable to couple to a plurality of transceivers via a plurality of transmission channels, transmit payload data via the plurality of transmission channels, and obtain monitored transmission conditions for one or more transmission channels in the plurality of transmission channels. During operation, the transmitter is further operable to generate reconfiguration request signals resultant from processing the monitored transmission conditions and transmit the reconfiguration request signals on transmission channels in the plurality of transmission channels.

PRIORITY CLAIM

This application is a continuation of application Ser. No. 13/956,922,filed 1 Aug. 2013, which is a continuation of application Ser. No.13/226,537 (now abandoned), filed 7 Sep. 2011, which is a continuationof application Ser. No. 11/860,329 (now abandoned), filed 24 Sep. 2007,which is a continuation of application Ser. No. 11/684,468, filed 9 Mar.2007 (now abandoned), the content of each of said applicationsincorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a data transmission method, acommunication system, a transceiver, a transmitter and a receiver.

BRIEF DESCRIPTION OF THE DRAWINGS

Hereinafter, exemplary embodiments of the invention will be describedwith reference to the drawings.

FIG. 1 is a schematic block diagram representation of a communicationsystem according to one embodiment of the present invention.

FIG. 2 is a schematic block diagram representation of a communicationsystem according to another embodiment of the present invention.

FIG. 3 is a flow diagram representation of a data transmission methodaccording to one embodiment of the present invention.

FIG. 4 is a schematic diagram illustrating a signal flow in a datatransmission method according to one embodiment of the presentinvention.

FIG. 5 is a schematic block diagram representation of a communicationsystem according to another embodiment of the present invention.

FIG. 6 is a schematic diagram illustrating a signal flow in a datatransmission method according to another embodiment of the presentinvention.

FIG. 7 is a schematic block diagram representation of a communicationsystem according to another embodiment of the present invention.

FIG. 8 is a flow diagram representation of a data transmission methodaccording to another embodiment of the present invention.

FIGS. 9A and 9B are flow diagram representations of data transmissionmethods according to embodiments of the present invention.

FIGS. 10A and 10B are schematic representations of symbols transmittedin data transmission methods according to embodiments of the presentinvention.

FIG. 11 is a schematic block diagram representation of a transmitteraccording to one embodiment of the present invention.

FIG. 12 is a schematic block diagram representation of a receiveraccording to one embodiment of the present invention.

FIG. 13 is a schematic block diagram representation of a receiveraccording to another embodiment of the present invention.

DETAILED DESCRIPTION

In the following, exemplary embodiments of the present invention will bedescribed in detail. It is to be understood that the followingdescription is given only for the purpose of illustrating the inventionand is not to be taken in a limiting sense. Rather, the scope of theinvention is defined only by the appended claims and is not intended tobe limited by the exemplary embodiments described hereinafter.

It is also to be understood that, in the following description ofexemplary embodiments, any direct connection or coupling betweenfunctional blocks, devices, components, or other physical or functionalunits shown in the drawings or described herein could also beimplemented by an indirect connection or coupling. While some of theexemplary embodiments will be described in the context of DSL technologybelow, it is to be understood that the various embodiments are notlimited thereto. Rather, the methods and devices described below may beapplied in other communication devices and methods, such as in wirelesscommunication.

It should be understood that the features of the various exemplaryembodiments described herein may be combined with each other, unlessspecifically noted otherwise.

The present invention relates to data transmission methods and devicesemployed in data transmission, such as communication systems,transceivers, transmitters and receivers.

FIG. 1 is a schematic block diagram representation of a communicationsystem 10, according to an exemplary embodiment of the invention. Thecommunication system 10 comprises a master controller 11, a plurality offirst transceivers 12 and a plurality of second transceivers 13. In theexemplary embodiment illustrated, the plurality of first transceivers 12is installed in a central office (CO) or local exchange, while theplurality of second transceivers 13 is installed in customer premises ascustomer premises equipment (CPE). Each of the first transceivers 12 iscoupled to one of the second transceiver 13 to transmit signals 20 inupstream and downstream directions.

Upon start-up of a first transceiver 12/second transceiver 13 pair, themaster controller 11 provides configuration parameters to the firsttransceiver 12 of the pair, which configuration parameters may includeinformation such as a service level of the subscriber, minimumguaranteed data transmission rate, maximum power spectrum or powerspectral density (PSD) available, or similar data. In an initializationphase, the first and second transceivers 12, 13 of the pair establishoperational parameters for various components of the transceivers 12, 13to improve data transmission quality. This may be effected, e.g., in ahandshake-phase between the first and second transceivers 12, 13.However, due to changing noise conditions, a change of the configurationoriginally specified may become desirable. For example, when the firstand second transceivers 12, 13 are connected by copper wire pairs in apair-wise fashion and several copper wire pairs are arranged proximal toone another, e.g. in the form of a wire bundle, changing noiseconditions may result from a larger number of subscribers going online,i.e., a larger number of first transceiver 12/second transceiver 13pairs establishing data transmission therebetween, resulting incross-talk between copper wire pairs.

To accommodate changing noise conditions/the first transceiver 12 andthe second transceiver 13 are equipped with monitoring circuits 14 and15/respectively. The monitoring circuits 14, 15 monitor transmissionconditions such as a signal to noise ratio/for upstream and downstreamdata transmission, respectively. The monitoring circuits 14, 15 alsoprovide information 19 on the monitored transmission conditions for therespective data connections to the master controller 11. The mastercontroller 11 comprises a master monitor 16 to collect the information19 on the monitored transmission conditions. Thus, the monitoringcircuits 14, 15, and the master monitor 16 in combination may performthe function of a monitoring device which monitors transmissionconditions for a plurality of first and second transceiver. The mastercontroller 11 further comprises a PSD management unit 17 to determinenew configuration parameters, e.g., a new maximum PSD or a new signal tonoise margin (SNRM), based on the monitored transmission conditions. Inone embodiment, the master monitor 16 and the PSD management unit 17 mayrespectively be implemented as dedicated special-purpose circuits. Inanother embodiment/the master monitor 16 and the PSD management unit 17may be implemented in software which includes instructions to direct aprocessor, e.g., the CPU of a computer, to perform the functions ofmonitoring transmission conditions and determining new configurationparameters.

The determination of the new configuration parameters for the variouspairs of the first and second transceivers 12, 13 may be effected by thePSD management unit 17 in various ways. In one embodiment t the PSDmanagement unit 17 determines a new PSD for each of the transceiverpairs which is online based on a model that takes into account thetransmission conditions between plural pairs of the first and secondtransceivers 12, 13. In one embodiment, the model may take into accountcross-talk between data communication channels, e.g., copper wire pairs,associated with different pairs of the first and second transceivers 12,13. Further, in one embodiment, parameters according to variouscriteria, such as increasing an average data transmission rate inupstream and/or downstream directions for a plurality of transceiverpairs, preventing data transmission rates to fall below the guaranteedminimum data transmission rates for a maximum number of transceiverpairs, or similar objectives.

Once the new configuration parameters have been determined for onetransceiver pair or for a plurality of transceiver pairs, the mastercontroller 11 provides a signal 18 to the first transceiver 12 of therespective transceiver pair, the signal 18 including information on thenew configuration parameters. Responsive to the signal 18, the first andsecond transceivers 12, 13 of the respective transceiver pair(s) may bereconfigured to the new configuration parameters. In one embodiment, thereconfiguration of the first and second transceivers 12, 13 may includeadapting an operation of various transceiver components to the newconfiguration parameters. As used herein, the term “configurationparameter” refers to any parameter which defines general boundaryconditions on an operation of a data transmission system and transmittedsignals. Examples of “configuration parameters” include bounds for a PSDthat may be employed to generate signals, the number of tones, tonespacing or bit allocation for discrete multi-tone (DMT) signals, minimumor maximum net data rates, signal to noise margins, or similarparameters. Further, the term “configuration” of a device, such as atransmitter, receiver or transceiver as used herein refers to a state inwhich this device operates in accordance with given configurationparameters. The terms “reconfiguration” or “reconfiguring” as usedherein refer to a change of a state to accommodate new configurationparameters. The term “operational parameters” as used herein inconnection with a device, such as a transmitter, receiver ortransceiver, or in connection with a component of such a device, refersto a parameter that influences operation of the respective device orcomponent. Examples of “operational parameters” include cut-offfrequencies of filters, amplifier gains of amplifiers, samplingfrequencies of analog to digital converters (AID converters), samplingtimes or other parameters of a time domain equalizer, parametersdetermining operation of a frequency domain equalizer, or similarparameters.

As will be explained in more detail below, according to embodiments ofthe present invention, the transceivers of a transceiver pair or atransmitter and a receiver may be reconfigured online. As used herein,the term “reconfigured online” relates to a reconfiguration that may beachieved without transition to a dedicated reconfiguration phase inwhich data transmission services are interrupted for a longer period oftime. In other words, according to embodiments of the present invention,a reconfiguration may be effected without requiring an interruption ofdata transmission services. Thus, according to various embodiments, thereconfiguration may be provided during “showtime,” when thetransmitters, receivers, or transceivers are operational for thecommunication of live, payload data.

FIG. 2 is a schematic block diagram representation of a communicationsystem 30 according to one embodiment of the invention, thecommunication system 30 comprising a first transceiver 31 and a secondtransceiver 36. The first transceiver 31 and second transceiver 36 may,for example, be implemented as a transceiver pair, as were the first andsecond transceivers 12, 13 in the communication system 10 of FIG. 1.

The first transceiver 31 comprises a control interface 32 to receiveinformation on new configuration parameters, a transmitter circuit 33, areceiver circuit 34, and a communications interface 35 to communicatesignals to and to receive signals from the second transceiver 36. Thesecond transceiver 36 comprises a communications interface 37 to receivesignals from and to communicate signals to the first transceiver 31, areceiver circuit 38 and an evaluation circuit 39. In an exemplary modeof operation, the first transceiver 31 receives a signal includinginformation on new configuration parameters or on bounds on newconfiguration parameters at the control interface 32, and thetransmitter circuit 33 generates a reconfiguration request signal 41based on the signal received at the control interface 32 and outputs thereconfiguration request signal 41 via the communications interface 35 tothe second transceiver 36, the reconfiguration request signal 41comprising information on the new configuration parameters or on boundson new configuration parameters. In one embodiment, the reconfigurationrequest signal 41 output from the first transceiver 31 contains the sameinformation as the signal received at the control interface 32. Inanother embodiment, a control circuit (not shown) of the firsttransceiver 31 may process the information on new configurationparameters received at the control interface 32 and may generate thereconfiguration request signal 41 based on the processed information.

The reconfiguration request signal 41 received at the communicationsinterface 37 of the second transceiver 36 undergoes standard signalprocessing by the receiver circuit 38, and the information on the newconfiguration parameters or the bounds on new configuration parametersis evaluated by the evaluation circuit 39. In one embodiment, theevaluation circuit 39 determines whether the second transceiver 36 iscapable of accommodating the new configuration parameters or suitableconfiguration parameters within the bounds specified by thereconfiguration request signal 41. The evaluation performed by theevaluation circuit 39 may be based on one or several of various otherdata sets that characterize, e.g., current configuration parameters,current transmission conditions, current operational parameters of thesecond transceiver 36, available ranges of operational parameters of thesecond transceiver 36, transmission conditions estimated for the newconfiguration parameters or similar parameters, as will be described inmore detail below.

Based on a result of the evaluation, the evaluation circuit 39 generatesa reconfiguration response signal 42 and outputs the reconfigurationresponse signal 42 via the communications interface 37 to the firsttransceiver 31. For example, when the evaluation circuit 39 determinesthat the second transceiver 36 cannot accommodate the new configurationparameters or the new bounds on configuration parameters, the evaluationcircuit 39 generates a reconfiguration response signal 42 to indicatefailure of the second transceiver 36 to accommodate the newconfiguration. When the evaluation circuit 39 determines that the secondtransceiver 36 is capable of accommodating the new configuration, itgenerates a reconfiguration response signal 42 which indicates that thenew configuration can be accommodated. The reconfiguration responsesignal 42 may comprise further information. For example, in oneembodiment, the reconfiguration response signal 42 may includeinformation on a specific set of configuration parameters selected bythe evaluation circuit 39 from a range of possible new configurationparameters.

In the first transceiver 31, the reconfiguration response signal isreceived and processed by the receiver circuit 34 which initiates areconfiguration of the transmitter circuit 33 based on thereconfiguration response signal 42. In one embodiment, the transmittercircuit 33 is not adapted to a new configuration when thereconfiguration response signal 42 indicates that the second transceiver36 is not capable of accommodating the new configuration. On the otherhand, the transmitter circuit 33 is reconfigured when thereconfiguration response signal 42 indicates that the second transceiver36 is capable of accommodating the new configuration.

In one embodiment, the transmitter circuit 33 and the receiver circuit38 may be reconfigured synchronously. The term “synchronously” may referto synchronization at the symbol or signal level. I.e., when thetransmitter circuit 33 and the receiver circuit 38 are synchronouslyswitched to a new configuration, the switching is respectively performedsuch that the receiver circuit 38 is switched to the new configurationwhen the first signal that is generated by the transmitter circuit 33based on the new configuration is to be processed. Similarly, when thetransmitter circuit 33 and/or the receiver circuit 38 comprise severalfunctional sub-units, switching of these sub-units may be performedsynchronously at the symbol level. To effect synchronous switching ofthe transmitter circuit 33 of the first transceiver 31 and of thereceiver circuit 38 of the second transceiver 36 to the newconfiguration, a specific signal or signal sequence may be transmittedto initiate the switching to the new configuration, or switching may beperformed upon transmission of a predetermined signal, e.g., asynchronization (sync) symbol.

It will be appreciated that the block diagram of FIG. 2 is onlyschematic and that the first and second transceivers 31, 36 may compriseother components as appropriate. For example, while the receiver circuit34 is shown to directly provide a control signal to the transmittercircuit 33 of the first transceiver in the exemplary embodiment of FIG.2, the first transceiver may comprise, e.g., a control circuit coupledto the receiver circuit 34 to receive data included in thereconfiguration response signal 42 and coupled to the transmittercircuit 33 to control the transmitter circuit 33 based on the datareceived. Similarly, the evaluation circuit 39 of the second transceiver36 does not need to be directly coupled to the communications interface37, but may also be coupled to the communications interface 37 via atransmitter circuit (not shown) of the second transceiver 36 to outputthe reconfiguration response signal. Further, the evaluation circuit 39may also be coupled to the transmitter circuit (not shown) of the secondtransceiver 36 to reconfigure the transmitter circuit upon transmissionof a corresponding reconfiguration request signal from the firsttransceiver 31 to the second transceiver 36, so as to reconfigure thetransmission system 30 in the transmission direction from the secondtransceiver 36 to the first transceiver 31. In an exemplary embodiment,the transmitter circuit 31 of the first transceiver 31 and the receivercircuit 38 of the second transceiver 36 may be reconfiguredindependently from the receiver circuit 34 of the first transceiver 31and the transmitter circuit (not shown) of the second transceiver 36. Inone embodiment, both a reconfiguration of the transmitter circuit 33 ofthe first transceiver 31 and of the receiver circuit 38 of the secondtransceiver 36 and a reconfiguration of the receiver circuit 34 of thefirst transceiver 31 and of the transmitter circuit (not shown) of thesecond transceiver 36 may be initiated by transmitting a reconfigurationsignal from the first transceiver 31 to the second transceiver 36.

FIG. 3 is a flow diagram representation according to one embodiment of adata transmission method. The method, which is generally indicated at50, may, for example, be performed by the communication system 30 of theexemplary embodiment of FIG. 2. At 51, a first transceiver and a secondtransceiver are initialized. In the operational state of the first andsecond transceivers, at 52, a reconfiguration request signal istransmitted from the first transceiver to the second transceiver, thereconfiguration request signal comprising information on a newconfiguration, e.g., in the form of new configuration parameters or ofbounds on new configuration parameters. For example, the reconfigurationrequest signal may comprise information on bounds of a new PSD. At 53,the reconfiguration request signal is evaluated at the secondtransceiver. At 54, it is determined whether the new configuration canbe accommodated by the second transceiver. If, at 54, it is determinedthat the new configuration can be accommodated by the secondtransceiver, at 55, the new configuration is acknowledged by the secondtransceiver, and, at 56, both transceivers switch to the newconfiguration. If, at 54, it is determined that the new configurationcannot be accommodated by the second transceiver, at 57, the newconfiguration is rejected by the second transceiver and, at 58, bothtransceivers continue operation based on the old configuration.

FIG. 4 shows a schematic diagram 60 illustrating a signal flow in acommunication system according to one embodiment of the presentinvention, the communication system 60 comprising a master controller61, a first transceiver 62 coupled to the master controller 61 and asecond transceiver 63 coupled to the first transceiver 62. The mastercontroller 61 performs management functions such as determining aconfiguration for the first and second transceivers 62, 63 upon start upof the first and second transceivers 62, 63, or determining a newconfiguration during operation of the communication system 60. In oneembodiment, the master controller 61 and first transceiver 62 may beinstalled in a central office, and the second transceiver 63 may beinstalled in customer premises with the first and second transceivers62, 63 being interconnected by a copper wire pair. While not shown inFIG. 4, the communication system 60 may comprise a plurality of firstand second transceivers with the master controller 61 performingmanagement functions for said plurality of first and secondtransceivers.

Exemplary signal flows in a configuration phase 64, an initializationphase 66, and an operation phase 69 are explained with reference to FIG.4. In the configuration phase 64, the master controller 61 provides asignal 65 including configuration parameters to the first transceiver 62while the first and second transceivers 62, 63 are in an idle state. Theconfiguration parameters provided as signal 65 may, for example, includean initial PSD. In the initialization phase 66, the master controller 61communicates a start-up signal 67 to the first transceiver 67. Inresponse thereto, the first transceiver 67 transmits the originalconfiguration parameters 68 to the second transceiver 63. The first andsecond transceivers 62, 63 then undergo a training phase in whichoperational parameters of the transceivers are adapted within the boundsimposed by the configuration parameters 68. By way of illustration, butnot limitation, the training phase during initialization may beimplemented as a handshake phase between a pair of DSL moderns.

In the showtime or live operational phase 69 of the transceivers 62, 63,when payload data is being transmitted between the first and secondtransceivers 62, 63, the data being generated is based on the originalconfiguration parameters 68. When the master controller 61 determinesthat reconfiguring the first and second transceivers 62, 63 isdesirable, it outputs a signal 70 including information on newconfiguration parameters to the first transceiver 62. As has alreadybeen explained above, the master controller 61 may output the signal 70based on various criteria. In one embodiment, the master controller 61outputs the signal 70 based on monitored transmission conditions betweena plurality of first and second transceiver pairs. In one embodiment,the signal 70 is output to accommodate dynamically varying noiseconditions due to cross-talk between data connections interconnectingdifferent first and second transceiver pairs. However, the signal 70 mayalso be output based on other criteria, e.g., a change in service levelfor the respective subscriber. Based on the signal 70, the firsttransceiver 62 transmits a reconfiguration request signal 71 to thesecond transceiver 63 where the reconfiguration request signal 71 isevaluated. The reconfiguration request signal 71 may, for example,comprise information on new configuration parameters, such as a new PSD,or on bounds on configuration parameters, such as a new maximum PSD.Based on the reconfiguration request signal 71, a response signal 72 isgenerated by the second transceiver 63 for transmission to the firsttransceiver 62, the response signal 72 indicating whether the secondtransceiver accepts or acknowledges the new configuration (acknowledge)or rejects the new configuration. When the second transceiver 63acknowledges the new configuration, the first and second transceivers62, 63 synchronously execute the transition to the new configuration at73. The transition to the new configuration is implemented synchronouslyat the symbol level, i.e., the first and second transceivers 62, 63undergo the transition upon processing the same symbol. The transition73 may be made at a predetermined time, e.g., upon transmission of async symbol. The first transceiver 62 then outputs a signal 74 to themaster 61 to indicate a transition to the new configuration (an oksignal) or to indicate that the transition has failed (a failuresignal). If the first and second transceivers 62, 63 have beenreconfigured, operation of the first and second transceivers 62, 63continues based on the new configuration parameters.

As may be seen from the schematic diagram of FIG. 4, according to oneembodiment, the reconfiguration of the first and second transceivers 62,63 may be achieved while the communication system is operational, i.e.,without a long interruption of data transmission services between thefirst and second transceivers 62, 63.

It will be understood that, while only one reconfiguration isschematically indicated in FIG. 4, the reconfiguration of the first andsecond transceivers 62, 63 may be repeated when required, so that thefirst and second transceivers 62, 63 may be repeatedly reconfigured foroperation under a variety of different configuration parameters.

FIG. 5 is a schematic block diagram representation of a communicationsystem 80 according to another embodiment of the invention. Thecommunication system 80 shown in FIG. 5 is based on the communicationsystem 30 of the exemplary embodiment of FIG. 2, but additionalcomponents are shown in the drawing to explain the operation of thecommunication system 80 in more detail. The communication system 80comprises a first transceiver 81 and a second transceiver 91. In anexemplary embodiment, the first transceiver 81 is installed in a centraloffice, while the second transceiver 91 is installed in customerpremises. In one embodiment, the first transceiver is coupled to amaster controller (not shown) similar to the one shown in FIGS. 1 and 4.

The first transceiver 81 comprises a control interface 82 to receive asignal containing information on a new configuration from the mastercontroller, a transmitter circuit 83, a communications interface 84 tocommunicate signals to the second transceiver 91, a control circuit 85coupled to the transmitter circuit 83 to control a configuration of thetransmitter circuit 83, and a receiver circuit 86 coupled to the controlcircuit 85 to provide data to the control circuit 85. For illustrativepurposes only, it will be assumed that the transmitter circuit 83generates DMT signals.

The second transceiver 91 comprises a communications interface 92 toreceive data from the first transceiver 81 and to communicate data tothe first transceiver 81, a receiver circuit 93, an evaluation circuit94 coupled to the receiver circuit 93, a register 95 to store anindicator of a transmission condition and coupled to the evaluationcircuit 94, a bit and gain controller 96 coupled to the receiver circuit93 and to the evaluation circuit 94, and a transmitter circuit 94. Thereceiver circuit 93 and the transmitter circuit 97 each may comprise aplurality of logical sub-units 93 a, 93 b and 97 a, 97 b, only two ofwhich are schematically indicated. Similarly, the transmitter circuit 83and the receiver circuit 86 of the first transceiver 81 may respectivelycomprise a plurality of logical sub-units (not shown in FIG. 5).

An exemplary mode of operation of the communication system is explainedwith reference to FIG. 5, assuming that the communication systeminitially already is in an operation state. When a reconfiguration ofthe first and second transceivers is required, information on newconfiguration parameters is received as a signal 101 at interface 82 ofthe first transceiver 81. Based on the signal 101, the control circuit85 inputs data 102 to the transmitter circuit 83 to control thetransmitter circuit 83 to generate and communicate a reconfigurationrequest signal 103. In one embodiment, the data 102 may be identical tothe data 101 received from the master controller. In another embodiment,the control circuit may process the data included in the signal 101 togenerate the signal 102. For example, when the master system providesdata 101 indicative of a maximum PSD, e.g., in the form of parametersthat specify the maximum PSD as a function of frequency, the controlcircuit 102 may determine the scaling factors for every tone of thespectrum and may provide the scaling factors as data 102 to thetransmitter circuit 83 which generates the reconfiguration requestsignal 103 based on the data 102. The reconfiguration request signal 103may comprise one or several DMT symbols, each of which may also comprisefurther data, e.g., payload data. In one embodiment, the data 102 istransmitted to the second transceiver 91 via an overhead channel forcontrol information, e.g., an overhead channel of an ADSL2/ADSL2+standard.

After processing the reconfiguration request signal 103 to retrieve thedata 102, the receiver circuit 93 of the second transceiver 91 transmitsthe data 102 to the evaluation circuit 94. The evaluation circuit 94retrieves data 105 related to a transmission condition or transmissioncondition parameters from the register 95, the transmission conditionparameters stored in the register 95 quantifying a transmissioncondition from the first transceiver 81 to the second transceiver 91 forthe present configuration. In one embodiment, the data 105 includessignal to noise ratios (SNRs) for different tones of the DMT spectrum asdetermined during transceiver training in an initialization phase. Basedon the data 105, information on the current configuration parameters andthe information on new configuration parameters contained in data 102,the evaluation circuit may estimate values for transmission conditionparameters anticipated for the new configuration parameters. In oneembodiment, the evaluation circuit extrapolates the transmissioncondition parameters stored in register 95 to estimate the anticipatednew transmission condition parameters. In one embodiment, theextrapolation may be linear in the scaling factors of the tones of theDMT spectrum. In various embodiments, more complex models may beemployed to estimate the new transmission condition parameters, e.g.,taking into consideration inter-symbol interference.

When the evaluation circuit 94 determines, based on the estimated newtransmission condition parameters, that the second transceiver 91 is notcapable of accommodating the new configuration parameters, it sends afail signal 106 via interface 92 to the first transceiver 81 to indicatethat the reconfiguration may not be effected. If the evaluation circuit94 determines that the second transceiver 91 is capable of accommodatingthe new configuration parameters, it sends the signal 106 via interface92 to the first transceiver 81 to acknowledge that the reconfigurationmay be effected. In an exemplary embodiment, the evaluation circuit 94determines new bit allocation values Bi and gain values Gi for everytone i of the DMT spectrum and provides the new Bi and Gi values 109 tothe bit and gain controller 96, and further includes the new Bi and Givalues in the acknowledge signal 106 for transmission to the firsttransceiver 81. After retrieving the new Bi and Gi values 107 from thesignal 106, the receiver circuit 86 of the first transceiver 81 providesthe new Bi and Gi values 107 to the control circuit 107 of the firsttransceiver.

At a predetermined time, the control circuit 85 controls the transmittercircuit 83 of the first transceiver 81 to generate signals based on thenew Bi and Gi values determined by the evaluation circuit 94 of thesecond transceiver 96. In an exemplary embodiment r the control circuit85 provides a control signal 108 to the transmitter circuit 83 or to aplurality of configurable sub-units of the transmitter circuit 83 toeffect the change to the new Bi and Gi values. Synchronously with thereconfiguration of the transmitter circuit 83 of the first transceiver81 r the bit and gain controller 96 directs the receiver circuit 93 ofthe second transceiver 91 to reconfigure the receiver circuit 93 to thenew Bi and Gi values r i.e., to the new PSD. In one embodiment r thetransmitter circuit 83 of the first transceiver 81 and the receivercircuit 93 of the second transceiver 91 may be switched to the new PSDwhen a sync symbol is transmitted r or switching may be initiated bytransmission of a specific symbol sequence.

According to one exemplary embodiment r switching of the transmittercircuit 83 and of the receiver circuit 93 to the new configuration maybe achieved without a dedicated training phase. In one embodiment roperational parameters of the transmitter circuit 83 and of the receivercircuit 93 may be adapted to the new configuration by extrapolation fromcurrent operational parameters. In another embodiment, the transmittercircuit 83 and the receiver circuit 93 may be trained utilizingpredefined DMT symbols that are transmitted from the first transceiver81 to the second transceiver 91, e.g., sync symbols, as will beexplained more fully below.

While only a reconfiguration for signal transmission from the firsttransceiver 81 to the second transceiver 91 has been described so far rthe reconfiguration of the transmitter circuit 97 of the secondtransceiver 91 and of the receiver circuit 86 of the first transceiver81 may also be initiated by the first transceiver 81. For example, uponreceiving information on a new PSD from the master controller atinterface 82, the control circuit 85 of the first transceiver 81 maydetermine new bit allocation values and gain values for the datatransmission direction from the second transceiver 91 to the firsttransceiver 81 and may transmit these new values to the secondtransceiver 91. In the second transceiver 91, the evaluation circuit 94reconfigures the transmitter circuit 97 to the new bit allocation andgain values. Upon transmission of the next sync symbol, or at anotherpre-defined time, the receiver circuit 86 of the first transceiver 81and the transmitter circuit 97 of the second transceiver 91 switch tothe new configuration. In one embodiment, the PSDs for upstream anddownstream data transmission directions may be changed independentlyfrom one another.

FIG. 6 is a schematic diagram illustrating a signal flow in acommunication system 120 according to another exemplary embodiment. Thecommunication system 120 comprises a master controller 121, a firsttransceiver 122 and a second transceiver 123. In one embodiment, thefirst and second transceivers 122, 123 may be implemented in the samemanner as the transceivers 81, 91 of the communication system 80 of theembodiment of FIG. 5. The master controller 121 and the firsttransceiver 122 may be installed in a central office, while the secondtransceiver 123 may be installed in customer premises. In an operationphase 124, the master controller 121 communicates a signal 125 to thefirst transceiver 122 when a reconfiguration of the first and secondtransceivers 122, 123 is desired, the signal 125 including informationon a new maximum PSD and a new SNRM. Based on this information, thefirst transceiver 122 determines new scaling factors (transmitted signalstrength indication, TSSI) for each tone of a DMT spectrum, asschematically shown at 126, and transmits a signal 127 includinginformation on the TSSI values and the new SNRM to the secondtransceiver 123. In one embodiment, the signal 127 is transmitted via anoverhead channel. Based on signal 127, the second transceiver 123estimates new signal to noise ratios for each tone of the DMT spectrum,as schematically shown at 128 and, at 129, calculates a new bitallocation value and gain value table, as indicated at 129. Depending onwhether the second transceiver 123 is capable of accommodating the newconfiguration, the new bit allocation value and gain value table istransmitted to the first transceiver as signal 130 and thereconfiguration is executed at 131, or the second transceiver 123rejects the new configuration at 132. The first transceiver 122communicates a signal 133 to the master controller 121 to indicate thatthe reconfiguration has been effected or that the reconfiguration hasfailed.

While specific exemplary implementations of communication systems andtransceivers according to various embodiments have been explained above,it is to be understood that all block diagrams of such devices andsystems shown in the drawings are only exemplary and that otherfunctional units may be included as appropriate. For example, while notshown in FIGS. 2 and 5, the first and second transceivers 31, 36 and 81,91, respectively, may also include monitoring circuits to monitortime-varying signal transmission conditions similar to the monitoringcircuits explained with reference to FIG. 1. Further, while variousfunctional sub-units of the transceivers explained above are shown asseparate entities in the drawings for illustrative purposes, any circuitor functional unit shown in the drawings may be comprised of severalfunctional sub-units. For example, in one embodiment, the transmitterand receiver circuits may respectively comprise a circuit to performanalog signal processing, e.g., analog filtering and A/D conversion, anda further circuit to perform various digital signal processingfunctions. Further, the various circuits, registers or other unitsexplained with reference to FIGS. 1-6 above may also be integrallyformed. By way of illustration, but not limitation, in one embodiment,digital signal processing paths of the transmitter circuit 83, of thereceiver circuit 86 and of the control circuit 85 of the firsttransceiver 81 of the embodiment of FIG. 5 may be implemented as asingle integrated circuit.

With reference to FIG. 7, a communication system 140 according toanother embodiment of the present invention is explained. Thecommunication system 140 comprises a transmitter 141 and a receiver 151.While not shown in FIG. 7, the communication system 140 may furthercomprise a master controller coupled to the transmitter 141 to provideinformation on a new configuration to the transmitter 141 via a controlinterface 142. In one embodiment, the information on the newconfiguration may be based on a monitored transmission condition betweena plurality of transmitters and receivers.

The transmitter 141 comprises the control interface 142, a transmittercircuit 144 to generate a signal based on data, a control circuit 143 tocontrol a configuration of the transmitter circuit 144, a register 145to store pre-defined data and to provide the pre-defined data to thetransmitter circuit 144, and a communications interface 146 coupled tothe transmitter circuit 144 to transmit signals generated by thetransmitter circuit 144 to the receiver 151. The transmitter circuit 144is configurable, i.e., it may be set to one of several differentconfigurations to generate signals having different characteristics. Byway of illustration, but not limitation, when the transmitter circuit144 generates DMT signals, the different configurations may correspondto different PSDs, different tone spacing, different numbers of tones orsimilar. As will be explained in more detail below, upon receivinginformation on a new configuration via interface 142, in one embodimentthe control circuit 143 may reconfigure the transmitter circuit 144 fromthe present working, showtime configuration to a new configuration whena signal is generated from the predetermined data stored in register145, and subsequently reconfigured back to the original operational,showtime configuration.

The receiver 151 comprises a communications interface 152 to receive thesignal 149 transmitted from the transmitter 141, a receiver circuit 153to process the signal, a control circuit 154 to control a configurationof the receiver circuit 153, and a training circuit 155 to train thereceiver circuit 153. The receiver circuit 153 is configurable, i.e., itmay be set to one of several different configurations to process signals149 having different characteristics. By way of illustration, but notlimitation, when the receiver circuit 153 processes DMT signals, thedifferent configurations may correspond to different PSDs, differenttone spacings, different numbers of tones, or similar variations. Aswill be explained in more detail below, in one embodiment the controlcircuit 154 may reconfigure the receiver circuit 154 from the presentshowtime configuration to the new configuration when a signal generatedfrom the predetermined data stored in register 145 is processed, andsubsequently back to the present showtime configuration. In oneexemplary embodiment, the training circuit 155 trains the receivercircuit 153 when the receiver circuit 153 is in the new configuration,i.e., processes a signal generated from the predetermined data. As usedherein, the term “training” refers to an adaptation of operationalparameters of the respective unit to adapt operation of the unit to anew configuration.

The following describes an exemplary mode of operation of thecommunication system 140. It will be assumed that the transmitter 141and the receiver 151 are in an operational, showtime state and arerespectively in a first configuration corresponding, e.g., to a firstPSD. When a master controller determines that a reconfiguration of thetransmitter 141 and the receiver 151 is desirable, information on thenew configuration, e.g., a new PSD, is input to transmitter 141 atcontrol interface 142 and is provided to the control circuit 143. Thecontrol circuit 143 stores the information on the new configuration andalso provides the information to the transmitter circuit 144 fortransmission to the receiver 151, e.g., utilizing an overhead channel.In the receiver 151, the information on the new configuration isprovided to and stored by the control circuit 154.

After transmission of the information on the new configuration to thereceiver 151, a retraining phase is initiated. In one embodiment, theretraining phase may be initiated by transmission of a specific flag orcontrol information. In another embodiment, the transmitter 141 andreceiver 151 may automatically initiate the retraining phase aftertransmission of the new configuration parameters.

In the retraining phase, the transmitter circuit 144 may remain in thefirst configuration when generating signals carrying payload data orspecific types of control signals. However, the control circuit 143switches the transmitter circuit 144 to a secondConfiguration—corresponding to the new configuration to which thetransmitter is to be Reconfigured—when signals generated from thepre-defined data stored in register 145 are generated and output. In oneexemplary embodiment, the signals generated based on the data inregister 145 may correspond to sync symbols. In another embodiment, thedata in register 145 may correspond to payload data that has beenpreviously transmitted and is retransmitted. Similarly, the receivercircuit 153 of the receiver 151 may remain in the first configurationwhen processing signals carrying payload data, while the control circuit154 may switch the receiver circuit 153 to the second configuration whenthe signals generated form the pre-defined data are processed. Thus, thetransmitter circuit 144 and the receiver circuit 153 may be repeatedlyand synchronously switched between the first and second configurationsto retrain the transmitter 141 and the receiver 151 for the new, i.e.,second configuration. After the retraining phase is completed, thetransmitter 141 and receiver 151 synchronously switch to the newconfiguration.

A data transmission method according to an exemplary embodiment isexplained with reference to FIG. 8, which is a flow diagramrepresentation of the method generally indicated at 160. At 161, atransmitter and receiver are initialized. In one embodiment, theinitialization may include training the transmitter and receiver for anoriginal configuration, e.g., an original PSD. At 162, the transmitterand receiver are operational and signals generated based on the originalPSD are transmitted from the transmitter to the receiver. At 163,information on the new PSD is provided to the transmitter and thereceiver. At 164, retraining of the communication system is started,with the retraining being performed on symbols that correspond topredetermined data and are generated based on the new PSD. At 165, thetransmitter and receiver switch to the new PSD.

According to one embodiment, in the retraining started at 164, onlyselected signals are generated based on the new PSD, while other signalscontinue to be generated based on the old PSD. The selected signals may,e.g., be sync symbols that are utilized to synchronize operation of thetransmitter and receiver. In other embodiments r the selected signalsmay include predetermined data. As used in connection with theembodiments of FIGS. 7 and 8, the term “predetermined data” refers todata that is known to the receiver even before transmission of thesignal, e.g., because the data corresponds to a fixed sequence of valuesas utilized in various control signals, or because the data has beenpreviously transmitted as in the case of payload data that isretransmitted. The predetermined data does not need to be fixed r butmay vary between successive signals that are generated based on the newPSD.

FIG. 9A is a flow diagram representation of a data transmission method170 according to another embodiment of the invention. The method 170may, for example, be employed in the method 160 of FIG. 8 to implementthe training process started at 164.

At 171, data to be transmitted is retrieved, e.g., from a bufferbuffering payload data or from a register or other memory which storespredetermined data, such as data corresponding to a sync symbol. At 172,it is determined whether the signal to be generated and transmitted is atraining signal. If it is determined that the signal is a trainingsignal, at 174, the signal is generated based on a new PSD and, at 175,is transmitted. If the signal is determined to be not a training signal,at 173, the signal is generated based on the old PSD, i.e., the PSD forwhich the transmitter and receiver are presently configured and, at 175,the signal is transmitted. In one embodiment, at least one signalgenerated based on the old PSD is transmitted before transmission of oneof the training signals, and another signal generated based on the oldPSD transmitted after transmission of this training signal. In oneembodiment, a plurality of training signals may be transmitted, apredetermined number of signals that are not training signals beingtransmitted in between successive training signals or in betweensub-sequences of training signals. In other words, according to oneembodiment, the generation of the signals may be repeatedly andperiodically switched between the old and new PSDs in the retrainingphase.

FIG. 9B is a flow diagram representation of a data transmission method180 according to another embodiment of the invention, which is based onthe method 170 of FIG. 9A. At 181, data to be transmitted is retrieved,e.g., from a buffer buffering payload data or from a register or othermemory which stores predetermined data, such as data corresponding to async symbol. At 182, it is determined whether the signal to be generatedand transmitted is a training signal. If the signal is no trainingsignal, it is generated based on the old PSD and so as to have a cyclicextension (CE) of a given length, e.g., the cyclic extension length forwhich the transmitter has been originally trained. When the signal is atraining signal, at 184 the signal is generated based on the new PSD andhaving a cyclic extension length that is different from the given lengthof the non-training signal cyclic extension. In other words, in themethod 180 of the exemplary embodiment of FIG. 9B, both the PSD and thecyclic extension length are switched between training signals andnon-training signals. In one embodiment, the cyclic extension may havean increased length when a training signal is generated. Similar to themethod of FIG. 9A, in the retraining phase the generation of the signalsmay be repeatedly and periodically switched between the old and new PSDsand, in combination therewith, between the two different cyclicextension lengths. As used herein, the term cyclic extension may includea cyclic prefix and/or a cyclic suffix. The term “cyclic extension” asused herein refers to any repetition of a part of a signal before and/orafter the main part of the signal, i.e., before and/or after the partcarrying payload data.

It will be appreciated that, in the methods 160, 170, and 180 of FIGS.8, 9A, and 9B, respectively, the old PSD and given cyclic extensionlength may be different from the PSD and cyclic extension length of theconfiguration established upon initialization. The PSD and cyclicextension length may be the PSD and cyclic extension lengthcorresponding to a preceding reconfiguration of the communicationsystem. In other words, the methods 160, 170, and 180 may also beemployed for repeated reconfiguration.

FIG. 10A is a schematic representation of a sequence of signalstransmitted from a transmitter to a receiver in a data transmissionmethod of, e.g., the exemplary embodiment of FIG. 9A. The sequence ofsignals is shown as a function of time. The signals, for example, may beOFDM symbols or DMT symbols. In an operation state 191, data symbols 201are generated based on an “old” PSD, i.e., a PSD that corresponds to thepresently active configuration of the communication system, sync symbols202 also being generated based on the old PSD and being periodicallytransmitted to effect synchronization of transmitter and receiveroperation. At a time 192, information on a new PSD is provided to thetransmitter and to the receiver utilizing, e.g., a channel of datasymbol 203. By providing the new PSD, the retraining phase is initiatedand starts upon transmission of a sync symbol at 193. In the retrainingphase, sync symbols 204 are generated based on the new PSD, while datasymbols 205 are still generated based on the old PSD. In other words,the PSD is switched from the old PSD to the new PSD when a sync symbol205 is transmitted, and back to the old PSD after transmission of thesync symbol. As will be explained in more detail below/the components ofthe communication system are trained for the new PSD based on thesymbols that are generated using the new PSD, i.e., training isperformed on the sync symbols 204. At 194/the retraining is completed.Retraining may be completed when, e.g., a predefined number of symbolshaving the new PSD has been transmitted, or when the training of thecommunication system components have sufficiently converged or meetpredefined quality standards. After completion of the retraining/datasymbols 207 also may be generated based on the new PSD, i.e., thecommunication system is fully switched to the new PSD.

FIG. 10B is a schematic representation of a sequence of signalstransmitted from a transmitter to a receiver in a data transmissionmethod of, e.g., the exemplary embodiment of FIG. 9B, and is generallysimilar to the sequence of FIG. 9A. One difference between the sequencesof FIG. 9A and FIG. 10B is that, in the retraining phase starting at 213and completed at 214, sync symbols 224 are generated based on a new PSDand have a cyclic extension of length C2 different from a cyclicextension length C1 of the data symbols 225 in the retraining phase.After completion of the retraining at 214/the communication system fullyswitches to the new PSD, i.e., also the data symbols 227 are generatedbased on the new PSD. The cyclic extensions of the data symbols 227 andof the sync symbols after completion of retraining have a length C3which may be identical to C1 or C2, or which may be different from C1and C2.

FIG. 11 is a schematic block diagram representation of a transmitter 230according to an exemplary embodiment of the present invention. Thetransmitter may be utilized, e.g., as transmitter 141 in thecommunication system 140 of FIG. 7. The transmitter 230 comprises aninterface 231 to receive data, e.g., from a subscriber terminal computeror a wide area network, and a transmitter circuit coupled to theinterface 231 to generate a signal based on the data. The transmittercircuit comprises a framer 232 to frame the data, an interleaver 233 tointerleave the framed data, a trellis code modulator 234 to performtrellis coding, a multiplexer 235, an inverse fast Fourier transform(IFFT) unit 236, a digital-to-analog (D/A) converter 237, and anamplifier 238. While one input of the multiplexer 235 is coupled to anoutput of the trellis code modulator 234, another input is coupled to aregister 240 which stores predetermined data, e.g., data correspondingto a sync symbol. Signals generated by the transmitter circuit areoutput at an interface 239. It will be appreciated that the functionalunits shown in FIG. 11 are only exemplary, and that other functionalunits, e.g., data buffers, a Reed-Solomon coder, filters etc., may beincluded in the transmitter circuit. Further, the various functionalblocks are shown as separate entities only for illustrative purposes,with it being understood that several or all of these elements may alsobe implemented in a single integrated circuit or a plurality ofintegrated circuits.

The transmitter 230 further comprises a control interface 241 to receiveinformation on a new configuration, e.g., from a master controllerinstalled in a central office. In one embodiment, the master controllermonitors noise conditions of a plurality of cables, e.g., cables in onebinder, and manages the PSD for a plurality of transmitter-receiverpairs based on the monitored noise conditions. The transmitter furthercomprises a control circuit 242 coupled to the interface 241 to receivethe information on the new configuration, e.g., on a new PSD. After theinformation on the new PSD has been received, the control circuit 242provides control signals 243 to various components of the transmitter230, namely the IFFT unit 236, the D/A-converter 237 and the amplifier238 in the exemplary embodiment of FIG. 11 to switch these componentsbetween two different operation states depending on whether a signal isto be generated based on the old PSD or based on the new PSD. Thecontrol circuit 242 is further coupled to the multiplexer 235 to controlthe active multiplexer input via a control signal 244 and to theregister 240 to control communication of the predetermined data from theregister 240 to the multiplexer using a control signal 245.

In one embodiment, the IFFT unit 236, the D/A-converter 237 and theamplifier 238 are controlled to generate a signal based on the new PSDwhen the active multiplexer input is the input coupled to the register240, i.e., the predetermined data is to be transmitted. In oneembodiment, the register 240 comprises a first portion 246 to store syncsymbol data and a second portion 247 to store copies of the sync symboldata for a cyclic extension, and the control circuit 242 controls theregister 240 to output data only from the first portion or from both thefirst portion and the second portion to the multiplexer 235 toaccommodate different cyclic extension lengths. In this manner, thetransmitter 230 of the exemplary embodiment of FIG. 11 may be employedto switch a PSD, with or without also switching a cyclic extensionlength, depending on whether or not a training signal is to betransmitted, as illustrated for the various embodiments explained withreference to FIGS. 8-10 above.

While not shown in FIG. 11, the transmitter 230 of FIG. 11 may alsoinclude a training circuit that is coupled to several of the functionalunits or blocks of the transmitter circuit to adapt operationalparameters of these functional units when signals are generated based onthe new PSD, thereby training the transmitter 230 for the new PSD.

FIG. 12 is a schematic block diagram representation of a receiver 250according to an exemplary embodiment of the invention which may, e.g.,be employed as receiver 151 in the communication system 140 of FIG. 7.The receiver 250 comprises an interface 251 to receive data from atransmitter and a receiver circuit 252 to process the data. Operation ofthe receiver circuit 252 is based on operational parameters stored in aregister 255. While the register 255 is shown as a separate entity inFIG. 12, it is to be understood that the register may be integrated withthe receiver circuit 252. Examples for operational parameters stored inthe register 255 include cut-off frequencies of filters of the receivercircuit 252, amplifier gains etc. The control circuit 253 controls theconfiguration of the receiver circuit 252 via control signal 254. In oneembodiment, the control circuit 253 controls the configuration of thereceiver circuit 252 so that, when a training signal generated based ona new configuration is to be processed, the receiver circuit 252 is alsoin the new configuration, but remains in the old configuration toprocess other signals that are not training signals.

In one embodiment, the new and old configurations correspond to new andold PSDs, the control circuit 253 controlling the receiver circuit 252to process signals having different PSDs. In one embodiment, the controlcircuit 253 controls the receiver circuit 252 to switch between thedifferent PSDs synchronously with the transmitter circuit. For example,when sync symbols are generated based on the new PSD, the controlcircuit 253 may control the receiver circuit 252 to switch to the newPSD for processing sync symbols.

The fully or partially processed training signals are provided to atraining circuit 257 which adjusts the operational parameters stored inregister 255 based on the signals. In one embodiment, the trainingcircuit may compare the fully or partially processed training signals tothe predetermined data based on which the training signals aregenerated, and may adapt the operational parameters in register 255based on the comparison. In one embodiment, the training circuit 257only adapts the operational parameters that are retrieved by thereceiver circuit 252 for operation according to the new configuration.

When retraining is completed, the control circuit 253 directs thereceiver circuit 252 to switch to and remain in the new configuration,so that the receiver circuit processes all signals received at interface251 based on the new configuration.

FIG. 13 is a schematic block diagram representation of a receiver 260according to one exemplary embodiment, showing an exemplaryimplementation of the receiver circuit. The receiver circuit comprises afilter 261, an automatic gain control (AGC), an AID-converter 263, atime domain equalizer (TEQ) 264, a cyclic extension remover 265, a fastFourier transform (FFT) unit 266, a frequency domain equalizer (FEQ) 276and further units 268 for additional digital signal processing. In theexemplary embodiment of FIG. 13, a control circuit 269 of the receiver260 is coupled to each of the units 261-267 to provide control signals270 to the units 261-267 in order to switch the receiver circuit betweendifferent configurations. For example, when different configurationscorrespond to different PSDs, the control circuit 269 may adjust acut-off frequency of the filter 261, a gain of AGC 262, a samplingfrequency of ADC 263, a cyclic extension length removed by cyclicextension remover 265, a tone spectrum of FFT unit 266, etc., based onwhether signals generated based on a first or second PSD are to beprocessed. In other embodiments, the control circuit 269 may be coupledto only a subset of the functional units schematically shown in FIG. 13to control their operation.

Register 281, 282, 284, 287 coupled to the filter 261, the AGC 262, thetime domain equalizer 264 and the frequency domain equalizer 267 storeoperational parameters for these units that specify operation of therespective units when switched to the new configuration for which thereceiver 260 is to be trained. By way of illustration, but notlimitation, the register 281 may store a filter cut-off frequency, theregister 282 may store an amplifier gain, and the registers 284 and 287may store coefficients or vectors indicative of the respective equalizerfunctions. Based on the processed training signals, the training circuit271 may update the values stored in registers 281, 282, 284, 287 totrain the receiver 260 for the new configuration. Upon completion of theretraining phase, the filter 261, the AGC 262, the time domain equalizer264, and the frequency domain equalizer 267 may continue operation basedon the new operational parameters stored in the registers 281, 282, 284,287 at this time.

The transmitter 230 of FIG. 11 and the receivers 250, 260 of FIGS. 12and 13 may respectively be installed at a near end or at a far end of adata transmission connection. For example, the transmitter and receivermay respectively be installed in a central office or in customerpremises. According to one embodiment, a transceiver may include both atransmitter 230 and a receiver 250 or 260 according to anyone of theembodiments described with reference to FIGS. 11-13 above. Pairs of suchtransceivers may be installed, e.g., in a central office and customerpremises. In one embodiment, the transceiver pairs may be interconnectedby copper wire pairs and may form a Digital Subscriber Line (xDSL)communication system. In one embodiment, the transmitter of a firsttransceiver installed in the central office and the receiver of a secondtransceiver installed in customer premises may be retrainedindependently from the receiver of the first transceiver and thetransmitter of the second transceiver. I.e., a reconfiguration ofupstream and downstream data communication may be performedindependently.

While the retraining of data communication devices has been illustratedas retraining on sync symbols with reference to FIGS. 8-13 above, itwill be appreciated that other symbols may be employed in theretraining. For example, specific sequences of sync symbols could bedefined to assist the training. In one embodiment, the PSD of the syncsymbols may vary during retraining, and may for example be graduallyadjusted from the old PSD to the new PSD.

While exemplary embodiments of the invention have been described above,it is to be understood that the present invention is not intended to belimited by these embodiments. In particular, it is to be understood thatany functional block or unit shown in the drawings and explained aboveis shown as a separate entity only for the purpose of betterillustrating the principles of the invention. However, the differentfunctional blocks do not need to be provided as separate units. Forexample, different functional units of a transmitter or receiver circuitmay be configured as an integrated circuit, e.g., those units performingdigital signal processing. In another embodiment, the monitoringcircuit, the control circuit or the evaluation circuit may be formed asan integrated circuit together with transmitter or receiver circuitcomponents.

Still further, the functionalities of the functional blocks shown in thedrawings and described above may be implemented by hardware, by softwareor a combination of both. Further, as used herein, circuits may beimplemented fully in hardware, or by a combination of hardware, softwareor firmware. For example, the transmitter and/or receiver circuits maybe configured so that they comprise a multi-purpose processor which isprogrammed so that it performs a part of the digital signal processingfunctions.

While a reconfiguration of data communication devices has been explainedin the context of a change in PSD for some of the exemplary embodimentsdescribed above, this description is only given for the purpose ofbetter illustrating the principles of the invention, and the presentinvention is not limited thereto. Rather, a reconfiguration may alsocorrespond to a change in any other configuration parameter(s), forexample a change in number of tones or frequency spacing for DMT signalsor bit allocation. Further, while some embodiments of the presentinvention have been described in the context of DSL systems, such asADSL, the embodiments of the present invention are not limited theretobut may also be applied in other communication systems, e.g., inwireless communication.

What is claimed is:
 1. A communication device, comprising a transmitteroperable configurable to: couple transmit payload data to a plurality oftransceivers via a plurality of transmission channels; transmit payloaddata via the plurality of transmission channels; during showtimeoperation, obtain monitored transmission conditions for one or moretransmission channels in the plurality of transmission channels; andduring showtime operation, generate reconfiguration request signalsresultant from processing the monitored transmission conditions, thegenerated reconfiguration request signals indicating bit allocationvalues a new transmitted signal strength indication, TSSI, and transmitthe reconfiguration request signals on at least one of the plurality ofthe transmission channels in the plurality of transmission channels tocommand cause at least one of the plurality of transceivers to changeits bit allocation values according to the bit allocation valuesindicated by the reconfiguration request signal and generate new payloaddata using the new bit allocation values and a transmitted signalstrength indication, TSSI, to be changed during showtime operation forat least one of the plurality of transmission channels withoutinterrupting showtime operation.
 2. The communication device of claim 1,wherein the monitored transmission conditions correspond to dynamicallyvarying noise conditions due to cross-talk between at least some of theplurality of transmission channels.
 3. The communication device of claim1, wherein the reconfiguration request signals indicate a new maximumpower spectral density.
 4. The communication device of claim 1, whereinthe reconfiguration request signals generated during showtime operationindicate a new signal to noise margin and the new TSSI.
 5. Thecommunication device of claim 1, wherein the communication device is aDSL modem and the reconfiguration request signals are transmitted on thetransmission channels in a downstream direction to the plurality oftransceivers.
 6. The communication device of claim 1, further comprisinga receiver operable to receive, during showtime operation and inresponse to the reconfiguration request signals, reconfigurationresponse signals on the transmission channels over which thereconfiguration request signals were transmitted, wherein thereconfiguration response signals indicate whether the at least one ofthe plurality of transceivers coupled to the communication device overthe plurality of transmission channels accepts or rejects a newconfiguration indicated by the reconfiguration request signals.
 7. Thecommunication device of claim 6, wherein the communication device is aDSL modem and the reconfiguration response signals are received on thetransmission channels in an upstream direction from the plurality oftransceivers.
 8. The communication device of claim 6, wherein thetransmitter is operable to transmit new payload data based on new bitallocation values and new gain values to each transceiver from which thereceived reconfiguration response signal indicates the transceiveraccepts the new configuration indicated by the reconfiguration signaltransmitted to that transceiver.
 9. The communication device of claim 6,wherein the transmitter is operable to reconfigure itself when thereconfiguration response signal received on one of the transmissionchannels during showtime operation indicates that the correspondingtransceiver accepts the new configuration indicated by thereconfiguration signal transmitted to that transceiver.
 10. A method ofoperating a communication device, comprising: transmitting payload databy a transmitter of the communication device to a plurality oftransceivers via a plurality of transmission channels; during showtimeoperation, obtaining monitored transmission conditions at thetransmitter for one or more transmission channels in the plurality oftransmission channels; and during showtime operation, generatingreconfiguration request signals by the transmitter resultant fromprocessing the monitored transmission conditions, the generatedreconfiguration request signals indicating bit allocation values a newtransmitted signal strength indication, TSSI, and transmitting thereconfiguration request signals from the transmitter to at least one ofthe transceivers on transmission channels in the plurality oftransmission channels to command at least one of the plurality oftransceivers to generate new payload data using the new bit allocationvalues and a transmitted signal strength indication, TSSI, cause bitallocation values to be changed during showtime operation for at leastone of the plurality of transmission channels without interruptingshowtime operation.
 11. The method of claim 10, wherein the monitoredtransmission conditions correspond to dynamically varying noiseconditions due to cross-talk between at least some of the plurality oftransmission channels.
 12. The method of claim 10, wherein thereconfiguration request signals indicate a new maximum power spectraldensity.
 13. The method of claim 10, wherein the reconfiguration requestsignals during showtime operation indicate a new signal to noise marginand the new TSSI.
 14. The method of claim 10, wherein the communicationdevice is a DSL modem and the reconfiguration request signals aretransmitted on the transmission channels in a downstream direction fromthe transmitter to the plurality of transceivers.
 15. The method ofclaim 10, further comprising receiving, during showtime operation and inresponse to the reconfiguration request signals, reconfigurationresponse signals by a receiver of the communication device on thetransmission channels over which the reconfiguration request signalswere transmitted, wherein the reconfiguration response signals indicatewhether the at least one of plurality of transceivers coupled to thecommunication device over the plurality of transmission channels acceptor reject a new configuration indicated by the reconfiguration requestsignals.
 16. The method of claim 15, wherein the communication device isa DSL modem and the reconfiguration response signals are received by thereceiver on the transmission channels in an upstream direction from theplurality of transceivers.
 17. The method of claim 15, furthercomprising transmitting new payload data based on new bit allocationvalues and new gain values from the transmitter to each transceiver fromwhich the received reconfiguration response signal indicates thetransceiver accepts the new configuration indicated by thereconfiguration signal transmitted to that transceiver.
 18. The methodof claim 15, further comprising reconfiguring the transmitter duringshowtime operation when the reconfiguration response signal received onone of the transmission channels indicates that the correspondingtransceiver accepts the new configuration indicated by thereconfiguration signal transmitted to that transceiver.
 19. Acommunication device, comprising: a transmitter operable to: couple to aplurality of transceivers via a plurality of transmission channels;transmit payload data via the plurality of transmission channels; obtainmonitored transmission conditions for one or more transmission channelsin the plurality of transmission channels; and during showtimeoperation, generate reconfiguration request signals resultant fromprocessing the monitored transmission conditions, the generatedreconfiguration request signals indicating a new transmitted signalstrength indication, TSSlbit allocation values, and transmit thereconfiguration request signals on transmission channels in theplurality of transmission channels to command at least one of theplurality of transceivers to change its bit allocation values accordingto the bit allocation values indicated by the reconfiguration requestsignal and generate a new transmitted signal strength indication, TSSI,cause bit allocation values to be changed during showtime operation forat least one of the plurality of transmission channels withoutinterrupting showtime operation; and a receiver operable to receive,during showtime operation and in response to the reconfiguration requestsignals, reconfiguration response signals on the transmission channelsover which the reconfiguration request signals were transmitted, thereconfiguration response signals indicating whether the at least one ofthe plurality of transceivers coupled to the communication device overthe plurality of transmission channels accepts or rejects a newconfiguration indicated by the reconfiguration request signals.
 20. Thecommunication device of claim 19, wherein the transmitter is operable totransmit new payload data based on new bit allocation values and newgain values to each transceiver from which the received reconfigurationresponse signal indicates the transceiver accepts the new configurationindicated by the reconfiguration signal transmitted to that transceiver.21. A communication device, comprising a receiver operable to: couple toa transceiver via a transmission channel; receive payload data via thetransmission channel; during showtime operation, to receivereconfiguration request signals resultant from processing the monitoredtransmission conditions, the generated reconfiguration request signalsindicating bit allocation values, and transmit the reconfigurationrequest signals on transmission channels in the plurality oftransmission channels to command at least one of the plurality oftransceivers to change its bit allocation values according to the bitallocation values indicated by the reconfiguration request signal andgenerate a new transmitted signal strength indication, TSSI, duringshowtime operation for at least one of the plurality of transmissionchannels without interrupting showtime operation.
 22. The communicationdevice of claim 21, wherein the monitored transmission conditionscorrespond to dynamically varying noise conditions due to cross-talkbetween at least some of the plurality of transmission channels.
 23. Thecommunication device of claim 21, wherein the reconfiguration requestsignals indicate a new maximum power spectral density.
 24. Thecommunication device of claim 21, wherein the reconfiguration requestsignals generated during showtime operation indicate a new signal tonoise margin and the new TSSI.
 25. The communication device of claim 21,wherein the communication device is a DSL modem and the reconfigurationrequest signals are transmitted on the transmission channels in adownstream direction to the plurality of transceivers.
 26. Thecommunication device of claim 25, further comprising a receiver operableto receive, during showtime operation and in response to thereconfiguration request signals, reconfiguration response signals on thetransmission channels over which the reconfiguration request signalswere transmitted, wherein the reconfiguration response signals indicatewhether the at least one of the plurality of transceivers coupled to thecommunication device over the plurality of transmission channels acceptsor rejects a new configuration indicated by the reconfiguration requestsignals.
 27. The communication device of claim 26, wherein thecommunication device is a DSL modem and the reconfiguration responsesignals are received on the transmission channels in an upstreamdirection from the plurality of transceivers.
 28. The communicationdevice of claim 26, wherein the transmitter is operable to transmit newpayload data based on new bit allocation values and new gain values toeach transceiver from which the received reconfiguration response signalindicates the transceiver accepts the new configuration indicated by thereconfiguration signal transmitted to that transceiver.
 29. Thecommunication device of claim 26, wherein the transmitter is operable toreconfigure itself when the reconfiguration response signal received onone of the transmission channels during showtime operation indicatesthat the corresponding transceiver accepts the new configurationindicated by the reconfiguration signal transmitted to that transceiver.